1. Field of the Invention
The present invention relates to an internal Universal Serial Bus (hereinafter “USB”) interface, and more particularly to an adaptive USB extender, wherein the USB extender is disposed to be mounted within a computer.
2. Description of the Prior Art
The advent of USB3.0 standard provides an ultra-high speed data transmission speed at 5 GHz, which can transfer data 10 times faster than the legacy USB 2.0 standard. In designing the USB3.0 subsystem, it is desirable to allow an integrated USB3.0 Extensible Host Controller Interface (hereinafter “xHCI”) controller to be proximate to the USB3.0 receptacle which can be reached by the user in an easy manner. This places a major challenge to maintain the signal integrity for this ultra-speed data transmission protocol.
Currently, the implementation for integrating a USB3.0 xHCI host controller in a computing machine is achieved by designing the 3.0 xHCI host controller at the motherboard level along with the USB3.0 receptacle, and introducing an add-on xHCI host card which is plugged into the Peripheral Component Interconnect Express (hereinafter “PCIe”) slots where the USB3.0 receptacle is physically placed and routed on the same printed circuit board (hereinafter “PCB”), and the xHCI controller is placed as well with minimal routing distance between the receptacle and its drivers.
Although the above implementation is the best way to maintain the signal integrity, but in real life it is utopian due to the mechanical constraints using such approach and the ability to place the USB3.0 receptacle in a convenient location for the user. First of all, USB3.0 signal is a very high speed signal with a data transmission rate at 5 GHz, and the 5 GHz data transmission signal is very hard to maintain the signal integrity if there is a signal discontinuity between the driver and the receiver. Therefore, the best mode to maintain signal integrity is to allow the USB3.0 receptacle to be close to the xHCI host controller chip and route the signal traces on the same medium, for example, printed circuit board.
To increase the flexibility of locating the USB3.0 receptacle in a computer, a USB extender is devised. An alternative configuration for the USB extender according to the prior art is shown in FIG. 1. FIG. 1 shows the configuration of a conventional USB extender 100. In FIG. 1, a USB3.0 receptacle 102 is located far away from a USB3.0 xHCI host controller 106 and is connected to the USB3.0 xHCI host controller 106 through a passive USB cable assembly 104. The xHCI host controller 106 is mounted on a PCIe interface 108 installed in a computing machine (not shown).
The present invention aims to introduce a way to maintain the signal integrity during the signal transmission along the USB cable assembly while preserving the flexibility of locating the USB3.0 receptacle in a computer.